Electrolytic processing apparatus



Dec. 5, 1950 c. w. HANGO'SKY ET AL 2,532,908

ELECTROLYTIC PROCESSING APPARATUS Filed Nov. 8, 1946 7 Sheets-Sheet l @QZ 1 f mw De 1950 c. w. HANGOSKY ET AL 2,

ELECTROLYTIC PROCESSING APPARATUS Filed Nov. 8, 1946 7 Sheets-Sheet 2 Ill/l/A L f h/afm q 52 Ly @amce WWW? Dec. 5, 1950 c. w. HANGOSKY EIAL ELECTROLYTIC PROCESSING APPARATUS 7 Sheets-Sheet 5 Filed Nov. 8, 1946 Dec. 5, 1950 c. w. HANGQSKY ET AL 2,532,908

ELECTROLYTIC PROCESSING APPARATUS Filed Nov. 8, 1946 '7 Sheets-Sheet 4- fl' /05 Md 4 44 Dec. 5, 1950 c. w. HANGOSKY ET AL 2,532,903

ELECTROLYTIC PROCESSING APPARATUS Filed Nov. 8, 1946 7 Sheets-Sheet 5 'I/ml lll w I J n 4 hl. 5 v aw S N. a 4 M w T 97 W l Dec. 5, 1950 c. w. HANGOSKY ETAL 2,532,908

ELECTROLYTIC PROCESSING APPARATUS Filed Nov. 8, 1946 7 Sheets-Sheet 6 A-C-ETCH Dec. 5, 1950 c. w. HANGOSKY ETAL 2,532,908

ELECTROLYTIC PROCESSING APPARATUS Filed Nov. 8, 1946 7 Sheets-Sheet '7 Patented Dec. 5, 1950 ELECTROLYTIC PROCESSING APPARATUS Clarence W. Hangosky, East Lansing, Mich, and

Garl S. Hornberger, Glen Ellyn, 111., said Hornberger assignor to Central Scientific Company,

a corporation of Illinois Application November 8, 1946, Serial No. 708,580

6 Claims.

Our invention relates to improvements in a process and apparatus for electrolytically treat ing metal surfaces with special reference to electrolytically polishing and etching the surfaces of metallurgical samples and other objects, the

general process and apparatus having been disclosed in U. S. patent application Serial No. 548,841 filed August 10, 1944, now abandoned, and Serial No. 697,765 filed September 18, 1946 in the name of Clarence W. Hangosky, the disclosures whereof, in so far as consistent herewith, being hereby incorporated and made a part hereof by reference.

An important object of our invention is the provision of a compact and efficient apparatus which, even in the hands of a relatively unskilled operator, will safely and consistently reproduce polished and etched surfaces of a superior character on many metals and alloys.

Further objectives include the provision of novel means for safely employing combustible or explosive reagents, for supplying various necessary electric currents having predetermined characteristics, and the provision of a new and improved cathode structure adapted to increase the quality of the etched or polished surface.

Other objects and advantages will become apparent from the following specification and from the drawings in which Figure 1 is a perspective view of our assembled device;

Figure 2 is a partially sectioned View of the processing unit of our device together with a portion of the housing therefor;

Figure 3 is a partially sectioned perspective view showing the relative disposition of the components;

Figure 4 is a partially sectioned top view of our processing unit;

Figure 5 is a section taken along the lines 5-5 of Figure 2;

Figure 6 is a partially sectioned top view taken along the lines 66 of Figure 2;

Figure 7 is a partially sectioned top view of a clamping device;

Figure 8 is a circuit diagram of the current supply and control means;

Figure 9 is a perspective view showing the processing unit removed;

Figure 10 is a vertical section of an explosion safety device; and

Figure 11 is an enlarged section of an object support and associated structure illustrated in Figure 2.

To obtain satisfactory and reproducible electrolytically polished and/or etched surfaces, particularly on metallurgical samples, it has been found necessary to control not only the current but also the character of the interface between the electrolyte and the sample or metal object which constitutes the anode of a suitable electric circuit.

In the present invention we obtain satisfactory control of the interface by supporting the sample or object to be treated over an aperture into which is directed a fountain of electrolyte carrying the etching or polishing current. The structure of our device and the arrangement of the component parts is such that there is imparted to the fountain of electrolyte at the point of contact with the sample a low and substantially even cross-sectional velocity which is characterized in free flow (i. e., when the sample is removed) by a substantially lat crest, and which provides means for uniformly and continuously eliminating from the interface bubbles formed during the process. Since some of the most dosirable reagents used in the preparation of elec trolytic solutions are inflammable, corrosive and, in some instances, explosive, we have incorporated mechanical and electrical safety devices conjunction with a novel electrical circuit to prevent accidental ignition 0r detonation of the electrolyte thereby allowing the practical use of these materials.

General organization These and other features have been embodied in a compactly arranged unit having a novel cabinet which houses the necessary regulating and supply means and provides convenient separation of the processing unit from the current supply apparatus when desired. The general organization and relationship of parts is best illustrated in Figures 1, 3 and 9, from which it may be seen that the processing unit, generally designated 2% includes frame 2? having parallel horizontal members 28 formed of angle iron or the like. A main cabinet frame, generally designated 2!, includes a pair of horizontal angle iron members 29 spaced to receive and slidably support the processing unit 25 by engagement with members 28 of the processing unit frame 27.

When assembled, the processing unit 20 is removably supported between left and right side housings 2t and 26, and in front of a main housing 22. An easel 23 extends upwardly from the main housing 22 above the processing unit 25, and in combination with the main housing 22 encloses a majority of the current supply and control apparatus. An apron is is interposed between the processing unit 28 and the main housing 22, and extends outwardly beneath the processing unit 28.

All of the elements essential to electropolishing or etching metal surfaces, except for current supply or control means, are included in the processing unit so, which may therefore be easily removed from the cabinet by slidingtheunit outwardly along the horizontal angle member 29 until free. This permits movement of the processing unit to practically any desired location for cleaning, inspection or use, power being supplied by flexible leads from the cabinet or other suitable source. Cooling water, if required by the nature of the electrolyte employed, can be conducted to the unit by flexible hose, but this is not always necessary.

Processing unit in general A horizontal plate iii of insulating material such as plastic or glass extends over the top of frame 2? and is surfaced with a suitably formed strip 32 of stainless steel. Other materials may, of course, be employed but due to the corrosive characteristics of reagents ordinarily employed in the process, materials resistant to such reagents should be selected.

A water jacket 33 of non-corrosive metal such as copper is attached to the frame 2'1 by bolts 35 extending through the frame 2i and through suitable lugs attached to the water jacket. The water jacket 33 is provided with an overflow spout 3i disposed adjacent itsupper edge, a drain cock and an inlet spout 39: which ex.- tends upwardly to the lip of the water jacket: and communicates with the interior through an open..- ing in the water jacket adjacent the bottom of the spout 39. A suitably shaped basket ll-l, formed for example of metal strips, fits into the: water jacket supporting a container d2 of non-corrosive material such as glass in contact with the under end of plate i and in spaced relation to the water jacket 33. A suitable gasket 53 may be interposed between the container l2 and the plate ii to form a tight seal. Anopening 453 through the plate 3i and strip 252 communicates with the interior of the container 2 and is closed by a light, loosely fitting disk 4-5; which prevents evaporation but is easily blown on if detonation of the electrolyte should occur, or if excessive pressure should otherwise develop within the container..

A water pipe 34 (Figure 4) having a valve 50 (Figures l and 3) extends outwardly from the main housing intov the processing unit 26' through an opening in a wall of a cup 45 and terminates in an orifice 41 forming an upwardly directed water fountain conveniently disposed for washing metal objects before or after processing. The bottom of the cup 35 is open and is disposed immediately over the spout 39 thus supplying cooling water to the water jacket around the container 42 Overflow from the water jacket 33 emerges from the overflow 5.? and is caught by an apron t8 which forms the front section of the main housing. The bottom of the apron se is provided with a drain 58 which may be connected with a sewer to dispose of the used cooling water. The. apron it extends forwardly and: upwardly beneaththe processing unit 4 in order to receive any electrolyte which might flow downwardly as a result of accidental fracture in the container 32.

A suitable cover 55 is provided with a lower flange 53 having openings loosely engaging pins 52 secured to frame 2!. Suitable detents are disposed on the cover to engage other members of the frame 2i for holding the cover in position in front of. the processing unit 20. A deflector 54 is attached to the inner surface of the cover 5| and protrudes into the space between the apron 43 and the lower surface of the water jacket 33 in order to deflect into the apron any liquid which may drip down between the processing unit and the cover M.

A pump, generally designated extends downwardly from the plate 3! into the electrolyte container 452 and may include a cylindrical tube 5'? supported by an upper cylinder plate 53. A propeller shaft 59 extends downwardly through the tube er and through an aperture 6! in the upper cylinder plate 58 terminating in a four-varied impeller which is surrounded by a cylindrical pump cylinder member A tube 8% is attached to the pump cylinder to conduct electrolyte from the pump upwardly to a cathode Cylinder $3 is closed by a bottom plate 5? having a small drain 83 formed therein. Two or more rods 69 having heads Tl extend upwardly throughv the lower plate 61,. the upper plate as, the plate 3i, and the strip 32 holding the component parts of the pump together with the tube El in contact with the plate 3!. Rods ee' are notched above the strip 32. as at iii to receive spring clips, 72, which support the rods.

Openings it are formed in the tube 5? immediately above the upper cylinder plate. 58 to permit the entrance of liquid. The tube 5? may also be notched to receive one or more anti.- vortex plates is which extend radially imvardly from the wall of the tube to approximately the boundaries of the aperture and serve todecrease the turbulence of. electrolyte within the tube 57 and the cylinder Preferably the joint between the, plate 3! and the tube 51' is not gas tight and the level or", electrolyte. in the container is maintained above the upper limit of the openings 23. thus preventing entrainment of gas in the liquid passing through the pump.

As will be apparent, liquid electrolyte is sucked into the pump tube 51 through the openings 7-3, and is then carried downwardly through the opening ill into the pump chamber where the impeller 52 forces the electrolyte with smooth even flow into the tube t l A cup-shaped processing chamber ll; having a series. of perforations. E? through the bottom thereof is provided with a threaded axial opening to receive the cathode Both the cathode 66 and the processing chamber ll'fi may be formed of a suitable metal such as lead,v Monel metal, stainless steel, or the like, adapted; tov conduct an electric current and to resist the corrosive effect of the electrolytic. solution. The cathode 6 includes a threaded body having an upper flange 78 which may be hexagonal to assist in inserting or removing the cathode, and a nipple it which extends downwardlybelow the processing chamber it and fits loosely within the tube at. An axial passageway 81 extends upwardly into the nipple l9 and the threaded body of the cathode 56' terminating in a, series of passageways 82 formed in an integral boss 33 which extends outwardly from the flange l8.

A tube 84 of insulating material such as glass fits over the boss 83 to conduct electrolyte upwardly from the cathode.

The passageways 82 may be three in number and are disposed at an angle to the axis of the tube 84 and to the axis of the passageway 8|. Thus an electrolyte is pumped through the oathode, any initial surge of liquid is directed against the walls of the tube 84 and not upwardly into possible temporary contact with an object S being treated. Since the upper end of the tube 84 is disposed in close proximity to the metal object S, it is obvious that the tube 84 must be filled before electrolyte can contact the object. Furthermore, when the angle of the passageways 82 with respect to the axis of the tube 84 is between approximately 20 and '70 degrees, the velocity imparted to the liquid adjacent the walls of the tube 84 is increased thus aiding in overcoming the inherent fluid friction adjacent the walls and assisting in the production of a fountain at the end of tube 84 which has a substantially equal upward velocity in every portion of its cross section. In practice, we have found that an angle of approximately 45 degrees is generally satisfactory, although as the length of the tube 84 increases sharper angles may be employed. While we prefer to employ a number of passageways 92, it is not to be understood that more than one is essential, nor is it essential that the passageways themselves be straight since curved passageways adapted to produce a spirally upward movement of electrolyte in the tube is permissible provided a cross-sectional velocity of the fountain is substantially constant.

It should b noted that the fit between the nipple l9 and the tube 64 need not be tight and a certain amount of electrolyte may be permitted to flow between the nipple and the tube in order to eliminate any air which may be unintentionally entrained therein by the pump 56. The surface of the boss 83 is preferably flat but may be slightly convex if desired. It is not essential that the surface be smooth or polished. Since the resistance of the electrolyte between the cathode 66 and the object S which usually forms the anode of the processing circuit affects the current flow, cathodes having bosses 83 of varying heights may be provided for insertion in the processing chamber 16 or the boss 83 may be removably attached to the cathode as by threads.

Object support and clamp A disk 86 having an aperture 81 extends over the top of the processing chamber I6 resting on gaskets 85 which are in turn supported by the plate BI and the strip of stainless steel 32. The processing chamber I6 is held in position against the plate 3I by screws 88 extending into suitably tapped holes in the walls of chamber I6. If desired, a gasket 89, preferably of insulating material such as rubber or plastic, may be interposed between the chamber I6 and the plate 3|. Since the screws 88 are in contact with the metal strip 32, it may be seen that an electrical contact is established between the cathode 66 and the strip 32 through the chamber I6.

A ring 9! is secured in position by screws 92 extending through the ring and into the chamber I and is provided with an inwardly extending flange 93 bearing against gaskets 8'? thus holding the disk 86 in position. The side walls of the aperture 81 taper upwardly, the minimum diameter of the aperture 81 at its upper surface being somewhat less than the internal diameter of the tube 84, which extends upwardly into close proximity but not into contact with the walls of the aperture 87. Channels 94 formed in the surface of the disk 86 extend radially from the aperture 81 to drains 96 permitting electrolyte flowing from the channels to drain downwardly through the perforations IT in the bottom of the processing chamber I6 into the container 42 for recirculation.

In the processing of a metal object, bubbles are generated at the interface of the fountain of the electrolyte and the object S which, if not removed, adversely affect the character of the etched or polished surface produced on the object. The continuous flow of electrolyte outwardly across the face of the object drives the bubbles outwardly and by entrainment with the electrolyte into the channels 94. Other entrained gas bubbles may follow the electrolyte escaping between the upper edge of the tube 84 and the walls of the aperture 81.

A motor support frame 9'! is secured to the plate 3| and to the strip 32 by suitable means and is provided with a spring clip 98 which supports a motor 99 connected to the propeller shaft 59. The support frame 9'! includes upper and lower flanges I 0| and IE2 having aligned openings in which is disposed a plunger I03 urged upwardly by a spring I04. The lower end of the plunger I03 contacts the plunger of a micro-switch I06 of the normally closed type mounted on the frame 91. An arm I0I having a horizontal leg I08 and a vertical leg I69 rigidly connected as by screws H5 is disposed above the plate 3|, the vertical leg I09 being pivotally secured to an angle iron III which is in turn secured to strip 32. Horizontal leg I08 is a channel member extending outwardly over the motor 99 and the motor support frame 91.

A vertical tube II2 extends through an opening formed adjacent the outer end of the horizontal arm I08 and is provided at its lower end with an insulating plug H3 suitably tapped to receive a contact screw H4. An anode wire II 6 is connected to the contact screw H4 and extends along the horizontal leg I08, terminating in a plug connector H1. The tube H2 is secured in place by a pair of suitably shaped dogs H8 disposed in the horizontal leg I98. One of the dogs H8 is threaded to receive a rod H9 which extends through the other dog terminating in an exposed knob I2I, as seen in Figure 7. Rotation of the knob I2I thus causes the dogs H8 to grip or release the tube H2 thereby permitting it to be raised and lowered as desired in order to bring the contact screw I I4 to a point adjacent the object S interposed between the contact screw H4 and the disk 86.

A transverse shaft I22 is journalled in the horizontal arm I08 and is provided with a rigid external handle I23 adapted to produce rotation of the shaft I22. A generally rectangular cam I24 having a rounded corner is secured to the shaft I22 and disposed to engage the plunger I03 operating the switch I06. The width of the cam I 24 is somewhat greater than the diameter of the plunger I03 so that in the absence of an object S, the weight of the arm I0! is transmitted through the cam I24 to flange IllI, depressing the plunger I03 to a corresponding level and holding the switch I06 open. Movement of the rectangular cam I24 moves the arm I0! about its pivot causing the contact screw I I4 to be raised and lowered, but as long as the cam I24 supports the arm I'It'i switch llleremainsi.open

regardless of the position of. the cam. Insertion of an. object S between the disk 36 and theacoru tact screw II4 supports the I81: thus removing the weightof the arm from the cam Hi l and permitting the. plunger Iilfi to riseunder the pressure. of spring. in as the cam I211 is rotated thus permitting: switch: IIIB' to close. A spring I25- secured. to angleiron lll'l andtoathe arm I'dil may be employed tosupp'lement the weight of the arm. Iiill and: thereby assist in clamping; the object S to the disk. 86

Since the switch .Ilit controls: the operation of the pump motor 39,. and cannot'close'tmless the sample is; in position under the contact screw IIfi', it isobviousthat-the motorfiil cannot operate the. pump until a sample: is: in. place, thereby preventing. the fountain of electrolyte from splashing through the aperture 81 into possible contact with. the: handsof the operator. p

Leads I27 extend from the motor 9-9 and switch I06 to the plug II'i; An; additional wire extends from the plug Hi to the strip 32 of stainless steel thereby establishing: a connection to the cathode '66 through. the processing chamber walls 16. To prevent accidental darnage; a chain I23 is connected to the plug and. to the strip 32 to withdraw the plug I I? from: its receptacle as the processing unit it is withdrawn from the frame 21. A suitable four-contact receptacle I2 9: for the plug II'I may be mounted on a plate I31 extending transversely across the main housing directly below the easel 23. Removable covers Itil having pins Iflfi-engaging clips H ll which are secured to the strip 32' extend outwardly from both sides of the arm: It? to the edge of the processing unit and are suitably shaped to enclose the motor 99 the motor support frame 8?, and disk 55, as well as wires'I I' fi and I 21;

Current suppfy and control Polishing, which-requires greater current than etching, is usually accomplished with direct cur:- rent, while etching may require either direct or alternating current. Our current supply means is therefore adapted to supply" either for closely controlled periods or time; Since: mostin.- stances alternating current is? available, we describe herein a circuit including rectiiying means, but it is" obvious that other current sources, such as a. D. generatormay be employed, eliminating. the rectifying. means: from the circuit. Also it should: be understood: that the terms anode and cathode are: used to designate the; two. electrodes, even. though in an A. C. circuit they of course. function. merely as electrodes.

Electrolytic polishing may in some. instances require currents on the order of. IOamps. at 200 volts, and since the electrolytic solution through which the current" flows is often combustible or explosive, it is obvious that adequate safietyprecautions must be" taken. As may be seen from the foregoing description, the circuit includes a fountain of electrolyteextendin from cathode to anode which is. renewed. for each. operation, thus creating an arcing condition as contact is made or broken which could causecombustion or detonation. Among our: novel circuit features is the provision of means which prevents the full current from flowing through. the. fountain as. contact with the object is being made or broken. Toprevent accidental completion of the circuit, or splashing of corrosive; electrolyte, means are provided to prevent? the formation of theiountair'r of electrolyte :unlessa. metal. obiect is properly positioned .for processing; The circuit units have also been: arranged. in such manner that both; of the operators hands are necessarily in a safe position during. processing, and. inaddition: the circuit provides: means for automatically preventing energizationor more tharrone main processing circuit at a time.

In general, the circuit includes a main. transformer I32 having a main: secondary I33 provided with-a grounded center tap I30. The secondary I33- supplies current to: paired half-wave rectifier tubes I34. The tubes, with associated choke coils i 36- and condensers I31, supply a highly rectified substantially linear direct-current to the anode contact I I Iand cathode 66, which is grounded. Each ofthethree principal circuits, namely, D. C. etch, D. C. polish, and A. C. etch includes a mainrela-y such as relays I38, I39, and I l-I, respectively, controlled by suitable timers I42, I43; and M4, respectively. The timers are adjustable by knobs I46, Hi7; and H58 (Figure l) and preferably are or the electronic type. Current control is obtained by sel'ector switches i i-Si and" IE1 connected to taps on opposite sides of the ground tap I30 on the main transformer secondary I33 and by a variable voltage transf'ormer- I52 in the A. C. etch circuit which operates from a secondary winding :53 on the transformer I32;

Suitable control knobs I54, I55 and I5'I are mounted on easel 23 and connected" to the selector switches Hit and I51 and to the variable voltage transformer I52. Selection of the desired circuit is obtainedin part through a normally open double throw gang switch I58 which 111.0118 position closes four contacts energizing the D. C. polishing circuit and in the other position closes four contacts energizing one of the two etching circuits. Selection of whether the etching is to be accomplished by alternate and direct current is obtained by a double throw snap type gang switch I59. Current for the timers I' l-2, M3, and I44, and for the switches I58. and I58 is obtained from a transformer IIiI having a secondary IE2 or from. a suitable secondary on the main transformer I321.

A normally open safety switch I63 is in series with the timers I42, I43, and ME and secondary I62, and. must beheld in closed. position by the operator to render any of the timer circuits efiective. Since both the switch I53 and the switch I63 will remain in: closed position only in response to hand pressure, it may be seen that by mounting: the switches more than one hands' span apart, as indicated in Figure the operators; hands will. be fully occupied during the process thus making it impossible to accidentally contact: the. anode or' the. electrolyte;

A low voltage: transform-er Hi l supplies current on the order of, say; 24 volts and of approximately 10 milliam-peres to a safety circuit which includes at: leastone' normally closed contact on the, relays I38, I39; and Mi, the anode contact" I14 the. cathode 661,. and. the coil' of. a relay IE5 whichxcontrols: circuits controlling the timers M2, I43, and- I44, andzthereforealso controlling the relays [38,1393: and: IAI'. As subsequently explained, when the processing; operation is started, all of the contacts of. relays I38, I39, and-I41; except the safety circuit contact, are open: and therefore the full: potential of the processing current does not exist between the anode and; the cathode-.: Asthe stream of electrolyte first contacts the object S which is in contact with the anode contact screw II4, the safety circuit is completed thus energizing the coil of relay I88. This relay in turn closes contacts permitting actuation of the timers I42, I43, and I44, which in turn actuate the main circuit relay I38, I39, and MI. Thus it may be seen that the potential between the anode and cathode at the time the fountain of electrolyte is first established is of such low voltage that no spark is generated as the circuit is completed thereby eliminating a possible cause of detonation or combustion of the eyectrolyte. The main circuit relays I 38 and I39 in their unenergized or normal position have three normally open and three normally closed sets of contacts and the relay MI in the A. C. circuit has two normally open and one normally closed pairs of contacts. Since the safety circuit includes the normally closed contacts of all three relays, it may be seen that energization of any one of the relays breaks the safety circuit and establishes the main circuit by closing the normally open pairs of contacts. The main circuit is maintained by a relay I61 until de-energized by one of the timers I42, I43, and I44.

A relay I18 controlled through the relay I61 by switches I58 and I59 normally directs current through the A. C. etch ammeter I69 and into the A. C. etch circuit. If, however, either D. C. polish or D. C. etch circuit is selected by switches I58 and I59, a circuit to the coil of the relay I18 is closed actuating the relay and thus connecting the D. C. power supply to the anode object S through lead I1I, D. C. etch ammeter I12, and D. C. polish ammeter I13. A main switch I16 is placed in series with the primary winding I18 of the main transformer I32 and is provided with a pilot light I11 across main leads I19 and I8I to indicate the condition of the circuit.

Assuming it is desirable to polish a metal object S and that a suitable solution has been placed in the container 42, the object is placed over the aperture 81 and the tube II2 lowered with the arm I81 in raised position until almost in contact with the upper surface of the specimen. The handle I23 is then moved towards the operator lowering arm I01 and permitting the anode contact screw II4 to come in contact with the object S. This supports the arm I81 permitting the switch I88 to close. Closing the switch I88 completes the circuit from the motor 99 to the cathode 96 through lead I82. Switch I16 is closed allowing current to flow through leads I19 and I8I and through the primary I18 illuminating the pilot light I11.

Operation To polish the specimen, the switch I58 is moved to the left, the position of switch I59 being immaterial in so far as the polishing circuit is concerned. The switch I58 is held in position with the right hand of the operator while the left hand closes safety switch I63. Selector switch I49 is adjusted to give the desired current and timer I43 is similarly adjusted to control the duration of treatment. As the switches I58 and I93 are closed, current fiows from transformer secondary I62 through lead I93 to blade I84 of the switch I58 to leads I86 and I81 to relay I18, leads I89 and I89 to ground. A lead I9I is also energized from the transformer secondary I62 completing a circuit through contacts I92 and lead I93 to motor 99. Operation of the motor establishes thejet of electrolyte which establishes electrical connection between the cathode 66 and the object S. This permits current to flow through the safety circuit energized by transformer I64 and extending through the coil of relay I88, lead I94, through the normally closed contact to relay I38, lead I98, the normally closed contact of relay I39, lead I91, the normally closed contact of relay I4I, and lead I98 to ground. The other side of the secondary of transformer I84 is connected by lead I99 to the object S thus completing the circuit.

Completion of the safety circuit, as previously explained, energizes the coil of relay I88 closing contacts 28! and completing a circuit including a lead I83, lead 282, the coil of relay I31, lead I86, a blade I84 of switch I58, lead I83, and transformer secondary I32 thus closing the contacts of the relay I81. A lead 203 establishes a connection between the coil of the relay It? and one of the pairs of contacts thereof to ground lead I89 thus permitting the relay I31 to remain closed regardless of the condition of the relay I83 which initially energizes the coil of relay I81.

Power input to the timers I42, I43, and I42 is obtained through leads 28c and 288 connected directly to, the secondary I52. Contacts 281 on switch I58 complete the circuit through the out put side of the timer I43 through lead 298, the contacts of relay I81, safety switch I83, lead 289, lead 2I I, timer I43, and lead 2 I2. A fourth set of contacts 2I3 in switch I58 completes the circuit to pilot light 2I4 which includes leads 285, lead 2I1, contacts 2I3 and lead I9I. Operation of the timer establishes a circuit through lead 2I8, the coil of relay I39, lead 2I9, and lead 2II back to the timer thus energizing the coil I39, opening the normally closed contact thereof to break the safety circuit, de-energize the coil of relay I85, and closing the three normally open contacts of the relay I39. The main secondary I33 of the main transformer I32 then passes current through the selector switch I49 through leads 22I and 222 through contacts of relay I39 through leads 223 and 224 through choke coils I35 and rectifier tubes I34. Filament current to the tubes I34 is obtained from a center tapped secondary 229 connected by leads 221 and 228 to the tubes I 34. Common lead 229 conducts the rectified current through lead 23 I, relay ammeter I13, lead I1I, relay I18, lead 232 to the anode S, through the fountain of electrolyte and to the cathode 66 which is grounded.

A voltmeter I14 is connected by lead 233 to the anode object S and the circuit continues through lead 234 to ground. When the desired time of treatment has been completed, the circuit established by the timer I43 through the coil of relay I39 is broken by the timer thereby deenergizing relay I39 and breaking the circuit. At the completion of the operation, the safety switch I53 and the gang switch I53 may be released, the release of switch I58 stopping the motor 99 and breaking the circuit through the pilot light 254.

Assuming further that the sample selected is to be etched by D. C. current, the desired etching current is set on selector switch I5I and the timer I42 set to give the desired etching time. The switch I58 is then thrown in the opposite direction and snap switch I59 thrown to D. C. etch. Closing of the switch I58 again energizes the motor 99 through lead I9I, contacts 239, lead I93, contacts I88 and lead I82. The safety circuit is energized in a manner previously described, the circuit through relay I81 being completed through leads I83, contacts 231, lead 238, contacts escapes 239 on switch :i::9,:lead lead 55135, the coil [of relay .1163, lead 283, through the zcontactscf relay 1183: to ground. Energirationof lead 518'! also actuates relay :I it, grounded by leads 138 land .1 .8 9.. The circuit to the timer 1 32 includes lead 2% extending from the timer to contacts 245 on switch 1:59, lead .235, contacts :242 onswitch 1.58,, leadlZllS, contacts onirelay tfil, lead 2891, .andlead 2| I. A pilot light :Zds. is energized by "lead 215, lead .265, vcontacts 24516 on switch 159, leadlfl, contacts 2% onswitch 158, and lead I!!! to transformer secondary Iii-2. Completion of the circuit through timer i152 closes relay i238 breaking the safety circuit and establishing the D. C. etch circuit through selector switch M9, leads 2 39 and 251, contacts of relay I38, leads 22 i and 223 to the rectifier tubes. The rectified current from the tubes flows through lead 229 through the contacts .of relay 1.38, lead 252, ammeter 1'52, lead ll|,.icontacts of relay Hi3, and lead 232 to the anode.

If, however, :a sample is required to .be etched by alternating current, the switch I58 may be left in the etching position and the snap switch I59 thrown in the other direction to establish the A. C. etch circuit. The timer his is energized through contacts 242, lead 2-35, contacts 2%, lead 255., lead 209, safety switch use, contacts of relay l67,';and lead 253. A pilot light 253 is also energized through lead me, lead 25?, contacts 25%, lead 259, lead 2 3?, contacts 2&8 and lead 1 9i. Actuation of the timer 14d establishes a circuit through lead .23! and '2 to the coil of relay Isl. Actuation of the-relay Mi breaks the safety circuit and establishes a circuit through secondary I53 .of'the main transformer I32, lead i252 and 2%, contacts oirrelay ass, lead 26 i, ammeter its, lead 'Zfiiithe .contacts of .unenergized relay 1-1-8, and lead i232 to the anode. The condenser 1-31 mayibe connected across leads 1'1] and I82 to cooperate with the choke coils 136 in smoothing the D. C. current output of tubes 134.

Although variations in the solutions employed cause variations in the resistance of the circuit and hence influence the current values, various general ranges maybe .cited as' illustrative of the desired conditions. The etching timers M2 and M4 should have an approximaterange of 0:5 to 3:0'seconds and the polishing timer- MS :a range of about 2 to 50 seconds. cuit, voltages of from 100 to 200 volts and from 0.5 to amps maybe required while each of the etching circuits should be capable of supplying 0:5 to 3 amps :at about 35 to "125 volts.

A solution generally adapted to etch and polish iron, steel and other metals may be prepared by mixing together 800 cc. of methyl alcohol containing 3% ether, 1 6 cc. of tap water, and :54 cc. of "70 to 72% perchloric acid. This solution, Whic'h'should be used at temperatures below 90 degrees and when used in conjunction with'a tube 85 having dimensions of approximately 1 A,," by millimeters bore will produce a circuit resistance of approximately '25 to 50 ohms which can'bc increased or reduced by changing the diameter of the "tube or the distance between the anode object S and the cathode 66.

As a specific example of a procedure for obtaining highly satisfactory results on low carbon steel, polishing may be continued for 10 seconds at room temperature using 3.4 amps at 120 volts. A sample of this metal polished as described may be etchedfby alternating current using 21 volts and 0:6 amps for ten seconds. Austenitic stainless steel may be satisfactorily polished fin 10 In the polishing 'cir- :11

seconds using 250 amperes at ".70 volts and rerritic stainless steel may be polished in 14 seconds using 2.8 .a-mperes .at volts.

The solutions herein described .are :only representative of many which may be employed. Other more violently explosive mixtures incorporating, for example, higher percentages cf perchloric acid and acetic anhydride ,nray be safely employed but glass 201' other inorganic materials'should be substituted for any plastic parts disposedto contact the solution. The :use of violently explosive mixtures such as these :emplaying high percentages of perchloric acid with acetic 'anhydride require the provision of additional safety means for "insuring the uninterrupited supply of electrolyte since even a temporary interruptioniin flow, as :for example that whichimight beacaused' by a large bubble, would break and perhaps subsequently reestablish the main circuit :at the anode thus producing an arcing condition between the object S and the electrolyte.

I therefore provide a float 261 having upwardly extending :arms 258 telescoped over a stem 269 having a head Ell disposed between the arms 2&3 and engageable thereby. The par-ts are disposed in :suchmanner that the arms 263' form a lost motion linkage with the stem 26,9 and the head 2H producing a downward motion of the stem 269 whenever the electrolyte in which the float 2b? is immersed drops below a predetermined level. The stem is connected to a suitable switch such :as switch M6 controlling the motor 99 and modified to permit actuation by downward movement of .the stemififi or a similar switch disposed in series with either the main. or timer circuits adapted :to stop the processing operation when such ievel -is reached.

.Since the processing unit includes the electrolyte container 32, pump 56, motor 99, arm ill-l, cathode cc, and all associated apparatus necessary to process metal objects except current supply and control means and cooling water, it is obvious'that the processing 2%} may be satisfactorily operated at a distance from the balance of the herein described .device. Flexible leads from socket I29 and a hose from pipe 44 may be used to supply current and water, or other more convenient sources' ofcurrent may be utilized. Furthermore, inspection and repair is greatly simplified because of the ease with which the processing unit 26 can be removed. This is accomplished by first removing the cover 5!, and then grasping the processing unit frame 21, drawing-it outwardly. The unit 2 6 slides outwardly like a drawer on members 28 and 29, the plug I i! being withdrawn by chain !28, and may be supported after withdrawal by the water jacket .33. Theplug .il] is the only mechanical connection between the processing unit 28 and the main frame 12!, since the water pipe M projects from main housing 22 into cup through an opening therein, but is not in any way mechanically attached to processing unit 22.

Our device may, of course, be simplified by using only one timer connected to the three circuits by suitable switches, and thepolishing circuit may be made to function as a direct current etching circuit, if desired. Greater accuracy and I ease of operation, however, is obtained by the use of separate circuits having independent control elements as described.

.Since the operation is purely mechanical, once the proper-current and time values have been determined, relatively unskilled labor can consistently'obtain highly satisfactory polished or polished and etched surfaces, the greatest economy of time being obtained in the polishing operation. Should occasion arise, the surface of the object can be plated, instead of polished, by reversing the direction of current flow and substituting a suitable solution for the electrolyte described. Since the cathode under such conditions becomes the anode, it should be formed of the metal being lated.

In the foregoing specification we have described in detail apreferred embodiment of our invention as required by R. S. i888, but it is not to be understood that in so doing we limit ourselves to the precise details, procedure and materials herein described except in so far as defined by the appended claims.

We claim:

1. In an apparatus for electrolytically treating metal surfaces, an apertured plate for supporting a metallic object to be treated, means containing a body of electrolyte beneath said plate, means for projecting a column of electrolyte from said body onto the exposed surface of the object overlying the aperture in said plate, a main circuit including said body of electrolyte, said column and said object arranged to pass an electric current between said column and said object across said exposed face of said object, a first relay having contacts included in said main circuit for controlling the latter, auxiliary circuit means actuated by the impingement of electrolyte upon said object for controlling said first relay to close said main circuit, whereby energization of said main circuit is dependent upon the column of electrolyte being in contact with said object, a transformer, means for producing a rectified direct current from the transformer, a second relay having contacts for connecting the rectified current to said main circuit, a control circuit including a timer for actuating said second relay, and a plurality of hand-operated switches in series in said control circuit, said switches being normally biassed to open position and being spaced apart a distance greater than can be spanned with a human hand.

2. In an apparatus for electrolytically treating metal surfaces, an apertured plate for supporting a metallic object to be treated, means containing a body of electrolyte beneath said plate, means for projecting a column of electrolyte from said body onto the exposed surface of the object overlying the aperture in said plate, an electrode arranged in the path of electrolyte projected from said body, and a hollow tube of insulating material extending from said electrode to a point adjacent the exposed surface of said object, said electrode having a passageway communicating with electrolyte projected from said body and with said tube, and at least that portion of said passageway adjacent said tube being disposed at an angle of approximately 45 to the axis of said tube.

3. In an apparatus for electrolytically treating metal surfaces, an apertured plate for supporting a metallic object to be treated, means containing a body of electrolyte beneath said plate, means for projecting a column of electrolyte from said body onto the exposed surface of the object overlying the aperture in said plate, a cathode electrode having a passageway for said column directed toward the exposed surface of said object, and a hollow cylindrical conduit extending from the aperture in said plate to said passageway,

14 said passageway having a smaller diameter than said conduit and being inclined at an angle of approximately 45 to the axis of said conduit so as to produce in said conduit a column of electrolyte having a substantially constant crosssectio'nal velocity.

4. In an apparatus for electrolytically treating metal surfaces, an apertured plate for supporting a metallic object to be treated, means containing a body of electrolyte beneath said plate, a cathode electrode located beneath said plate and having a passageway in communication with said body of electrolyte in said containing means, a hollow insulating tube telescoped over said electrode for conducting electrolyte emanating from said passageway onto the exposed surface of the object overlying the aperture in said plate, means for projecting electrolyte from said body into the passageway, and a plurality of connecting passages leading from said passageway and into said tube, said passages being disposed at an angle of approximately 45 to the axis of said tube.

5. In an apparatus for electrolytically treating metal surfaces, an apertured plate for supporting a metallic object to be treated, means containing a body 0f.e1ectrolyte beneath said plate, a first electrode disposed within said containing means for contacting electrolyte therein, a second electrode spaced from said first electrode and located outside said containing means for contacting the object supported by said plate, means for projecting a column of electrolyte from said body towards the object supported by said plate, a main circuit including said electrodes, said body of electrolyte, said column and said object arranged to pass an electric current between said column and said object, a relay control circuit including a relay having contacts, said contacts being included in series with said main circuit to control the flow of current therein, and a switch responsive to the level of electrolyte in said containing means, said switch being in said relay control circuit and in series with the coil of said relay whereby to interrupt said main circuit when the level of electrolyte in said containing means drops below a predetermined level.

6. In an apparatus for electrolytically treating metal surfaces, an apertured plate for supporting a metallic object to be treated, means containing a body of electrolyte beneath said plate, a pump for projecting a column of electrolyte from said body onto the exposed surface of the object overlying the aperture in said plate, a clamp adjacent said plate for urging the object to be treated against said plate, switch means controlled by said clamp and arranged to energize said pump only when an object is urged by said clamp against said plate, a main circuit including said body of electrolyte, said column and said object arranged to pass an electric current between said column and said obiect across said exposed face of the object, a relay having contacts included in said circuit for controlling the latter, and auxiliary circuit means actuated by the impingement of electrolyte upon said object for controlling said relay to close said main circuit, whereby energization of said main circuit is dependent upon the column of electrolyte being in contact with said object.

CLARENCE W. HANGOSKY. CARL S. HORNBERGER.

(References on following page) 'The fellow'ing referenees are of recerd in the CITED file (if this paAten-t:

UNITED STATES .PATENTS Number Name .Date Hartman Dec. 14, 1909 Smith Feb. 23, 1-915 Woodbury Nov. 2-6, .1918 Bailey May '23, 1922 Howe Mar. 10, 51923 Bohlman June 16, 19-31 Nov. 1, 1932 Jones July-18, 1933 Number Number Name Date Sweeney Dec, '19, 1933 Schlotter Aug. 30, 1938 Pri-tchard Aug. 11, 1942 Anderson May 18, 1943 FOREIGN PATENTS Country ,Date Great Britain Sept. 18, 1930 OTHER REFERENCES Metal Progress, August 1942, pages 209 to 212, article entitled Simplified Electro-Polishing of SteelSpec'imens, by Parcel. 

1. IN AN APPARATUS FOR ELECTROLYTICALLY TREATING METAL SURFACES, AN APERTURED PLATE FOR SUPPORTING A METALLIC OBJEC TO BE TREATED, MEANS CONTAINING A BODY OF ELECTROLYTE BENEATH SAID PLATE, MEANS FOR PROJECTING A COLUMN OF ELECTROLYTE FROM SAID BODY ONTO THE EXPOSED SURFACE OF THE OBJECT OVERLYING THE APERTURE IN SAID PLATE, A MAIN CIRCUIT INCLUDING SAID BODY OF ELECTROLYTE, SAID COLUMN AND SAID OBJECT ARANGED TO PASS AN ELECTRIC CURRENT BETWEEN SAID COLUMN AND SAID OBJECT ACROSS SAID EXPOSED FACE OF SAID OBJECT, A FIRST RELAY HAVING CONTACTS INCLUDED IN SAID MAIN CIRCUIT FOR CONTROLLING THE LATTER, AUXILIARY CIRCUIT MEANS ACTUATED BY THE IMPIGEMENT OF ELECTROLYTE UPON SAID OBJECT FOR CONTROLLING SAID FIRST RELAY TO CLOSE SAID MAIN CIRCUIT, WHEREBY ENERGIZATION OF SAID MAIN CIRCUIT IS DEPENDENT UPON THE COLUMN OF ELECTROLYTE BEING IN CONTACT WITH SAID OBJECT, A TRANSFORMER, MEANS FOR PRODUCING A RECTIFIED DIRECT CURRENT FROM THE TRANSFORMER, A SECOND RELAY HAVING CONTACTS FOR CONNECTING THE RECTIFIED CURRENT TO SAID MAIN CIRCUIT, A CONTROL CIRCUIT INCLUDING A TIMER FOR ACTUATING SAID SECOND RELAY, AND A PLURALITY OF HAND-OPRATED SWITCHES IN SERIES IN SAID CONTROL CIRCUIT, SAID SWITCHES BEING NORMALLY BIASSED TO OPEN POSITING AND BEING SPACED APART A DISTANCE GREATER THAN CAN BE SPANNED WITH A HUMAN HAND. 